The invention relates to preparation of creamy, calcium-fortified yogurt. In its more preferred aspects, it provides yogurt products having less fat than those prepared with whole milk, yet which have higher calcium contents and consistencies reminiscent of whole milk products.
Consumer interest in weight control and healthy eating is driving food processors to increase their offerings of foods having reduced fat contents and high nutritional value. Yogurt is perceived as a healthy food for a number of reasons. It is natural, contains calcium derived form milk and is associated with healthy digestion and other benefits. Typically, yogurt has a fat content only as high as cows milk, from which it is most often made. Even so, many health-conscious consumers would want even lower fat contents and even higher calcium contents. Unfortunately, the removal of fat decreases the smooth texture and nice color associated with yogurt, and the addition of calcium has caused a number of problems, including gritty mouthfeel and reduced protein heat stability.
While a number of efforts have been made to address these interrelated problems, the art is in need of effective solutions.
Yogurt has been prepared for centuries in essentially the same way. It was reportedly developed out of the need to preserve milk in warm climates like the Middle East. See, for example, Hui, Dairy Science and Technology Handbook, Vol. 2., Product Manufacturing, 1993, pp. 1-5. As originally developed, it has been considered a health food, but there is interest in reducing its fat content and/or increasing its calcium content. However, these modifications have proved to be significant technical challenges.
Yogurt is prepared by heating milk sufficiently to inactivate microorganisms in it, cooling from the high temperature, inoculating with a suitable culture (e.g., adding a small amount of a previous batch of yogurt), holding at a temperature near ambient or just above for long enough (e.g., 3 to 6 hours) for the active cultures to produce enough acid to coagulate the milk, and then cooling the resulting yogurt. A natural consequence of the culturing process is the production of lactic acid. The acid has several benefits, including creating a smooth, creamy texture, providing a clean, fresh taste and aiding preservation. If the yogurt is made with good manufacturing practices and cultured until the pH is less than about 4.6, the product should be stable for several weeks under refrigeration. Thus, maintaining the natural culturing process and results are important.
U.S. Pat. No. 5,449,523 to Hansen, et al., identifies a number of problems with adding calcium to yogurt. The patent indicates that some sources of calcium can cause grittiness and that others can cause the protein in milk to coagulate during heat treatment. Their solution to the problem involves adding chelating and/or alkaline agents, in addition to a calcium supplement, to maintain the pH above 6.7 prior to pasteurization. They were unable to identify any calcium supplement that did not require at least some change in the yogurt manufacturing procedure.
Attempts by the prior art to reduce fat in yogurt have also been met with technical challenges. By definition, yogurt must contain at least 8.25% milk-solids-non-fat before the addition of any bulky flavors. The milkfat content of regular yogurt must be at least 3.25%. (21 C.F.R. xc2xa7131.200) When either lowfat yogurt (21 C.F.R. xc2xa7131.203) or nonfat yogurt (21 C.F.R. xc2xa7131.206) is prepared, the fat content is reduced, thereby reducing the total solids and making the yogurt thin and watery. Various food additives have been identified to return the rheological properties and mouthfeel of these products to those of their full-fat counterparts. Widely used among these are whey and whey protein concentrates. Whey is the dried residue of the liquid obtained by the separation of curd in cheese making. Whey protein concentrate is a product obtained from whey wherein whey is xe2x80x9cmodified by partial or complete removal of lactose and or minerals, to increase the nonfat solids content of the foodxe2x80x9d (e.g., see 21 C.F.R. xc2xa7131.203(d)).
It is common for whey and/or whey protein concentrates to be employed along with other stabilizers such as gelatin, starch, vegetable and synthetic gums and the like. These materials as a group tend to increase the smoothness of the yogurt and decrease syneresis. An ideal stabilizer would yield a yogurt product which at the time of making and to the end of its shelf life, was the same in taste and texture as a full-fat, natural yogurt. The stabilizer should be easily mixed and should not adversely affect processing, flavor or texture. Stabilizers as currently available, however, do not significantly increase the calcium content.
There remains a need for a yogurt stabilizer and process for utilizing it that improves yogurt texture and increases the calcium content without adversely affecting taste, processing or product stability.
It is an object of the invention to provide a yogurt product with enhanced texture.
It is another object of the invention to provide a yogurt product with increased calcium content.
It is another object of the invention to provide a yogurt product having an enhanced smooth and creamy texture.
It is still another object of the invention to provide a yogurt-based product or ingredient with enhanced texture and/or calcium content.
It is another and more specific object of the invention to provide a process for preparing yogurt products having reduced fat contents, without sacrificing the viscosity and mouthfeel of yogurt prepared from whole milk.
It is yet another and more specific object of the invention to provide a process for preparing low-fat yogurt products exhibiting viscosity and mouthfeel reminiscent of yogurt prepared from whole milk.
It is another and more specific object of the invention to provide a process for preparing yogurt products having increased calcium contents, without causing processing, texture or stability problems.
It is yet another and more specific object of the invention to provide a process for preparing high-calcium, low-fat yogurt products exhibiting viscosity and mouthfeel reminiscent of yogurt prepared from whole milk.
These and other objects are achieved by the present invention, which provides a process for preparing a yogurt having an improved texture and containing active cultures, comprising: admixing milk with a modified whey characterized, on an as is basis, by a calcium content of at least 3%, protein content of from 10 to 20%, and a phospholipid content of at least 2% and a yogurt culture; holding the culture at a temperature and for a time effective to produce yogurt. The process is applicable to yogurt made from whole milk or meeting the standards for lowfat or nonfat products. The products prepared in the above manner are unique in composition and properties.
Many of the preferred aspects of the invention are described below.
Industrial Applicability
The following description will illustrate the preparation of preferred yogurt products according to the invention. The processing will be described in terms of the procedures effective for the materials employed in the various formulations.
The term xe2x80x9cyogurtxe2x80x9d is used herein to mean all of those products meeting the definition as set forth in 21 C.F.R. xc2xa7xc2xa7131.200, 131.203, and 131.206. Of the above sections, 21 C.F.R. xc2xa7131.203 specifically relates to lowfat yogurt and 21 C.F.R. xc2xa7131.206 specifically relates to nonfat yogurt. The invention improves the production of products of these types by providing better body and added calcium. For lowfat and nonfat products, the invention provides more of the body and mouthfeel of regular full-fat yogurt than has been achievable using ingredients described in the prior art.
The preferred products of the invention contain live and active cultures, as is required by the definition agreed to by the National Yogurt Association. Generally, these products are made by fermenting milk or a milk mix with a symbiotic blend of Streptococcus salvarius (e.g., subsp. Thermophilus) and Lactobacillus debruechii (e.g., subsp. Bulgaricus). See Hui, Dairy Science and Technology Handbook, Vol. 2., Product Manufacturing, 1993, pp. 1-55, and the references cited therein for a more detailed description, which is hereby incorporated by reference. The result is a semisolid fermented product having clean taste, a smooth texture and quick melting action in the mouth. Unlike prior art products, those of the invention contain more calcium and can be made with less fat while retaining a texture close to that desired of full-fat yogurt products.
Basic to all of the embodiments of the invention is a xe2x80x9cmodified wheyxe2x80x9d, which is defined as a whey fraction characterized, on an as is basis, by a calcium content of at least 3%, protein content of from 10 to 20% (more narrowly, 12 to 18%), and a phospholipid content of at least 2%. The calcium content is in highly soluble form and is homogeneously dispersed therein, as can be obtained by codrying a mixture containing the calcium, protein, fat and sugar components separated In these amounts to form the whey fraction. Calcium in this form is distinguished from calcium added as a salt that is simply mixed In dry form with whey. Preferred forms of modified whey are further characterized as conforming to the following analysis, based on a 100 gram sample.
This form of modified whey differs greatly from either sweet whey or whey protein concentrates and isolates, principally in the noted characterizing features set out above, and the ratios given directly below. Typical calcium to phosphorous ratios are within the range of from about 2:1 to about 10:1, e.g., about 5:2. Similarly, typical calcium to protein ratios are within the range of from about 1:4 to about 4:5, e.g., about 1:3. And, typical calcium to fat (essentially as phospholipid) ratios of from about 3:1 to about 10:1, e.g., about 4:1.
Products meeting these specifications can be prepared from whey by fractionation and drying to obtain the noted composition. Modified whey defined in this manner, derived from dairy products by fractionation, is believed to have its superior affects on yogurt prepared in accord with the invention because the high calcium content is complexed with other dairy components. Modified whey products of this type are commercially available, for example, under the trademark VersaPRO (e.g., grades B, C, D, E, M, N, S) from Davisco Foods International, Inc., Le Sueur, Minn.
A modified whey of this type is employed in an amount effective to improve the creaminess of the final yogurt. Preferred amounts will be at least about 0.25% based on the total weight of the formulation not counting bulky flavorings, and preferably within the range of from about 0.5 to about 2%. Preferred levels in lowfat and nonfat products are within the range of from abut 0.50 to about 1.25% on the same basis. Preferred products have calcium contents such that each serving contains from about 25 to about 50% of the Daily Value figure of 1000 mg per day.
The process of the invention entails treating milk containing the above form of modified whey to otherwise conventional processing. This is a surprising advantage of the invention. The milk is selected from any of the sources suitable and approved by the regulations, mixed with the modified whey and other additives such as flavors, sweeteners and stabilizers. The milk, or a milk mix containing other permitted ingredients, is heated under conditions effective to inactivate any organisms or enzymes. The milk or milk mix is then inoculated with a suitable culture (with a symbiotic blend of Streptococcus salvarius and Lactobacillus debruechii) and held for a time sufficient to develop the typical yogurt texture and taste. Holding at near 30 to 45xc2x0 C. for from 3 to 6 hours is typical. The final pH will typically be less than 5.0 (e.g., within the range of from about 4.2 to about 4.6). Following this step of culturing, the yogurt is cooled to slow down the culturing but not kill the culture.
The source of the milk can be any of those sources as by tradition, regulation or standard have come into favor. Principal among these are milk from cows, sheep, goats, buffalo, and the like. The milk can be fresh or in other forms permitted by regulation, including milk mixes with non-fat dry milk or the like. Various other materials can also be added to the milk mix prior to fermentation so long as they do not adversely affect the final quality of the yogurt or change its identity. For simplicity In description, the term xe2x80x9cmilkxe2x80x9d as used herein is also intended to include culturable milk mixes as permitted by regulation. The yogurt prepared according to the invention can be packaged plain or with sweeteners or flavors.
A sweetener is optional, but can be a sugar, sugary material or other sweetener, such as any of the high intensity sweeteners known to the art. The sweeteners can be employed directly in the milk or as part of a bulky flavoring that is added after fermentation. Bulky flavorings can be added to the bottom of individual containers in which the yogurt is cultured and ultimately distributed, or can be mixed into the yogurt following culturing. The bulky flavoring can be on the bottom of the container, sundae style, custard style or striped, as called for by the consumer interest desired.
Among the sugars are the mono-saccharides, di-saccharides and polysaccharides and their degradation products; e.g., pentoses, including aldopentoses, methylpentoses, keptopentoses, like xylose and arabinose; a deoxyaldose like rhamnose, hexoses and reducing saccharides such as aldo hexoses like glucose, galactose and mannose; the ketohexoses, like fructose and sorbose; disaccharides, like lactose and maltose; non-reducing disaccharides such as a sucrose and other polysaccharides such as dextrin and raffinose; and hydrolyzed starches which contain as their constituents oligosaccharides.
Among the intense sweeteners are acesulfame-K, aspartame, cyclamates, dihydrochalcone, saccharin, stevioside, thaumatin and the like. Also, low-intensity, low-calorie sweeteners such as sorbitol and erythritol can be employed.
Other ingredients may also be employed to impart their characteristic effects to the compositions of the present invention. Typical of such ingredients are flavoring agents, colorants, vitamins, minerals, and the like. Various flavors can be added directly to the milk prior to culturing if they do not interfere with the culturing process or afterwards if they would. Suitable flavoring agents can be employed to impart vanilla, cream, chocolate, coffee, maple, spice, mint, butter, caramel, fruit and other flavors.
When a bulky flavoring or sweetener is added to the yogurt after fermentation, the natural consistency of the yogurt is modified and it becomes necessary to add stabilizers of a type and in an amount sufficient to restore a natural yogurt-like texture. Stabilizers can also be added prior to naturally setting the yogurt for the purpose of enhancing smoothness and decreasing syneresis during long periods of storage. Typical of the stabilizers are proteinaceous materials such as gelatin, pectin, and whey protein concentrate, natural and synthetic hydrophilic colloids, such as carboxymethyl cellulose, vegetable gums such as locust bean gum, carob bean gum, guar gum, carggeenans and alginates and various starches and modified starches. The stabilizers are typically added prior to fermentation to assure thorough mixing with least affecting natural texture.
Tests have indicated that when bulky flavoring materials are to be mixed in with the yogurt subsequent to fermentation, the texture will be broken but can be essentially reestablished by utilizing effective amounts of stabilizers such as gelatin and/or starch, preferably before pasteurization. The starch and gelatin should be employed in amounts sufficient to restore a semisolid texture. It is an advantage of the invention that a very nice yogurt texture with a clean flavor can be achieved.
The following Examples are provided to further illustrate and explain a preferred form of the invention and are not to be taken as limiting in any regard, Unless otherwise indicated, all parts and percentages are by weight.